<p>Precision fertigation involves the precise application of water and fertilisers at optimal doses and frequencies, tailored to the weekly needs of the crops. In the present study, the existing VegSyst model was (i) adapted for soilless crop fertigation and (ii) validated for dry matter production (DMP) and uptake of macronutrients N, P, K and Ca in cucumber and tomato crops. The adaptation consisted of applying the VegSyst model together with climate forecast and a greenhouse climate model to predict the dry matter production of the greenhouse crop, and subsequently apply a simplified version of the Penman-Monteith (P–M) equation to predict the crop irrigation requirements, enabling nutrient requirements to be tailored to expected weather conditions. To validate the performance of the model, three experiments were conducted in a soilless greenhouse, cultivating cucumber and tomato crops. Two fertigation treatments were employed: (a) a conventional approach, reflecting the prevailing regional practice, where plants received a nearly constant nutrient concentration throughout the cultivation period, and (b) an improved approach adjusting nutrient concentrations on a weekly basis based on weather predictions and the predicted crop nutrient uptake. The primary objective of the model is to support its integration into a decision support system, providing greenhouse farmers with a tailored nutrient recipe aligned with crop requirements. This integration aims to mitigate water and nutrient waste in agriculture. Notably, in real-case scenarios, deploying the model led to a remarkable increase in agronomic efficiency. Simultaneously, there was a reduction in nitrate and phosphate leaching in the cucumber trials (up to 22% and 40%, respectively), without compromising overall productivity.</p>